Choosing a replacement PLC I/O module is straightforward once you know what to look for. This guide walks through the five checks that guarantee the right part.
The part number on the module's front label (e.g., 6ES7 322-1HH01-0AA0) is always the safest match. Photograph both the module and the PLC rack configuration and send them to us — we verify compatibility free of charge.
Digital (DI/DO) modules switch on/off signals; analog (AI/AO) modules handle ranges like 4–20mA or 0–10V. They are never interchangeable — check the symbol and wiring on your existing module.
Relay outputs switch AC loads and are volt-free; transistor (sinking/sourcing) outputs switch DC loads; triac outputs switch AC loads at higher frequency. Your load type decides which you need.
Count the channels (8, 16, 32...) and note the rated voltage (24V DC, 120/230V AC). A 16-channel 24V DC module will not replace a 32-channel relay module.
For S7-300 and similar systems, the module must fit the rack slot and be supported by your CPU's firmware. Send the CPU model with your inquiry — we confirm it.